Related Stories

Traces of a rare and pristine form of stardust that pre-dates our Solar System have been captured for the first time high above the Earth, confirming the key role of silicates in rocky planet formation.

An American team led by Dr Scott Messenger of Washington University in St Louis, Missouri, report their discovery of grains of interstellar silicate dust in today's issue of the journal Science.

Using a sensitive new French device known as the NanoSIMS probe, the researchers analysed interplanetary dust particles - fragments of comets and asteroids - collected 20 km above Earth in the stratosphere by NASA research aircraft.

Each particle is made up of thousands of grains from different parts of space. While most of the grains had been heated and processed in the formation of the Solar System and had lost their original stellar identity, a few had not.

Silicates are made of silicon and oxygen and make up a large proportion of the Earth. By measuring the ratios of different isotopes of oxygen, the researchers identified six grains of silicate stardust from outside the Solar System, and also identified what kind of mother star they had come from. This information helps scientists to tell what conditions were like when our Sun formed.

"We are in the game of trying to figure out where the stuff we're made of came from," he told ABC Science Online. "This kind of research can help us figure out what the environment was like when the Sun collapsed and formed our planets."

He said it can also help answer questions such as how similar the processes of planet formation elsewhere in the universe are to those that led to the creation of Earth. One of the puzzles to date has been that evidence for the importance of silica to planet formation has been apparently conflicting.

"We've seen these silicate grains in the spectra of stars that are forming planets now, but the perplexing problem is that we have not found silica dust in meteorites that come down," said Lineweaver. Thanks to the new study, evidence from telescopes was now consistent with physical evidence under the microscope.

"You are a mixture of a whole bunch of stars, and wouldn't it be nice to be able to say most of me came from that star there, and you could point to it out there in the sky," he mused. "We still can't do that, but with all this nice new evidence, we're starting to be able to do that. That's important because it's kind of like knowing who your grandparents are, except you're talking about stars rather than human beings."